High-altitude airships can be used as platforms for a variety of missions, including weather and astronomical observations. High-altitude airships are designed to be lightweight and hold large volumes of lifting gas to provide the desired amount of buoyancy in the upper atmosphere. A stratospheric balloon or airship is generally designed with a light-weight hull to contain lifting gas while minimizing overall airship mass. For example, airships intended for operation in the upper stratosphere may have a hull with a thickness that is less than 50 μm and an areal density less than 100 g/m2 of effective hull surface area, with a surface area on the order of tens of thousands of square meters.
The large surface area and thin hull can make the airship vulnerable to damage, particularly during launch. To launch an airship, a suitable launch site is selected and a launch window is selected when little or no wind is anticipated. The launch method restricts the amount of slack balloon material that is subject to wind drag or “sail” effect during the launch. The launch site also includes a large open area where the balloon can be laid out and inflated without risk of the fragile hull coming into undesirable contact with external objects. Here, the bulk of the balloon is laid out lengthwise on a suitable launch surface. Very large balloons (20-40 million cubic feet displacement; 500,000 to 1,000,000 cubic meters displacement) can use 800 ft (240 meters) or more of layout space. The top portion of the balloon is placed under a roller arm of a launch vehicle. This launch vehicle confines the lifting gas to the top portion of the balloon during inflation. At the completion of inflation, the launch arm is released and the balloon rises vertically over a payload release vehicle. This payload release vehicle includes a crane that suspends the payload. The payload release vehicle can be driven downwind to minimize the wind effects on the hull. Even with these precautions, these launch techniques can only be used in calm or near calm winds and still result in a significant risk of the hull and/or payloads being damaged. Further, these operational constraints severely limit the locations and times that a high-altitude balloon can be launched.
Throughout the drawings, identical reference numbers designate similar, but not necessarily identical, elements.